The entire point of stealth aircraft is to minimize the “visibility” to any enemy sensors. This includes radar and thermal sensors as well as good old fashion Mark One Eyeballs.

Here’s an interesting analogy. When you drive down a normal street at night your headlights reflect back from the road and you can see the street. Add a recent rain with water covering the ground and the street isn’t as visible because the light is absorbed or scattered by the water.

That’s essentially what stealth does, it redirects or absorbs radar waves. In addition, a good stealth design will hide the engine in the engine inlets and minimize the heat signature from the engine’s exhaust. Anything that is potentially radar reflecting (like bomb racks and bombs) will be carried internally. Finally, most stealth aircraft have a radar absorbing coating.

This funny looking faceted airplane is Lockheed’s F-117. The reason it looks so strange is because the facets (flat surfaces) are designed to reflect radar waves away from the radar antenna.

Before the first prototype was developed, they put a ten foot scale model on a pole 1,500 feet away from the radar antenna to test its stealth capabilities. When they turned the radar on the operator turned to the program manager (Ben Rich) and said, “Your model must have fallen off of the pole because I don’t see anything.”

Nope, it was still on the pole. That’s stealth at work.

Interestingly, at that moment a crow landed on the ten foot model and the radar operator then said that he could “see” it after all. The radar couldn’t detect a ten foot model but it did get radar returns from a crow 1,500 feet away.

But it isn’t really a Star Trek like “cloaking device.” Given the right orientation, radar can be reflected so the mission routings for this attack bomber were designed such that the aircraft avoided flying in a way that radar might be reflected at the enemy’s antennas. As a result, the routing to the targets were often circuitous.

One negative aspect of this aircraft’s strange aerodynamic design was that it was naturally unstable and as such had a flight computer that helped fly the aircraft.

The F-117 is no longer in service, but all other stealth aircraft are designed on basic stealth principles.

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